VMkernel(Purpose-build operating system to run virtual machines) is the most critical component of vSphere ESXi Hypervisor. vSphere ESXi runs directly in memory. Any error in it can potentially crash the host and also the virtual machines running on the host. To avoid this situation and to provide greater resiliency and also to protect the host against memory errors, vSphere ESXi hypervisor can utilize the Reliable Memory Technology, a CPU hardware feature through which a region of memory is reported from the hardware to vSphere ESXi hypervisor as being more reliable. This information can be used to optimize the placement of the VMkernel and other critical components such as initial thread, hostd and the watchdog process. This Reliable Memory technology helps to guard the ESXi hypervisor against memory error.

With the prior versions of vSphere 5.5 (vSphere 5.1 and eralier), The balanced policy for host power management  leverage only the performance state (P-State). Which helps to keep the processor running at a lower frequency and voltage. With vSphere 5.5 , the deep processor power state (C-state) also used to provide additional power savings. Another potential benefit is improved performance with reduced power consumption because Turbo mode frequencies on Intel chipsets can be reached more quickly while other CPU Cores in the physical  package are in deep C-states.